A synchronous motor with permanent magnets generally includes a polyphase stator, made up of one or several coils per phase and a stack of metal sheets making up a magnetic circuit, and a rotor with one or several permanent magnets. Furthermore, in order to determine the angular position of the rotor relative to the coils, sensors are generally positioned on the stator to detect variations of the rotary field induced by the rotor. In practice, these sensors are often angularly offset relative to the coils, for bulk reasons. These sensors in particular deliver information required to be able to generate control signals governing the operation of the motor, but also to determine the position of the rotor (number of revolutions performed, end of travel position, intermediate position, blocked position detection).
In order to generate the control signals of the motor, it is common practice to position, within the stator of the motor, a number of sensors strictly equal to the number of phases of the stator. For example, in the case of a three-phase stator, three Hall effect sensors are in most cases arranged within the stator. The use of a number of sensors strictly equal to the number of phases of the motor is, however, restrictive in terms of bulk and cost.
With a view to reducing the number of sensors used to manage the operation of a synchronous motor with permanent magnets, document U.S. Pat. No. 6,163,117 describes a method for generating control signals that makes it possible to decrease the number of sensors. The disclosed principle amounts to replacing one of the actual sensors with a virtual sensor, i.e., generating an output signal of a fictitious sensor by computation, based on signals provided by the real sensors, which are present in a number smaller than the number of phases. It appears, however, that the disclosed control method does not make it possible to generate control signals for the operation of the motor to be optimized. The method in particular does not offer any flexibility to account for the different possible operating ratings of the motor and optimize the operation of the motor in each of these operating ratings.